1. Field of the Invention
The present invention relates to cavity-backed slot antennas, and particularly to low-profile cavity-backed slot antennas using a uniplanar compact photonic band-gap substrate.
2. Description of the Related Art
Cavity-backed slot (CBS) antennas have been extensively investigated for applications to airborne and satellite communications, because they satisfy the requirements of flush mounting, low cost and light weight. The cavity height is usually designed to be one-quarter wavelength or three-quarters of a wavelength at the resonator frequency in order not to destroy impedance matching, since the backing conductor is transformed to an open circuit in shunt with the slot. The cavity volume can be reduced through dielectric loading, but the bandwidth and efficiency will also be reduced.
Applications of photonic band-gap (PBG) materials to antennas have been presented for leakage modes suppression. Recently proposed uniplanar compact PBG (UC-PBG) structures exhibit a distinctive stopband and have been exploited to reduce surface wave of patch antennas.
There is a need in the art for low-profile flush-mounting antennas for airborne and satellite applications. There is further a need in the art for cavity-backed slot antennas with reduced cavity volumes, and particularly with low profile cavities, but without a loss of efficiency. There is further a need in the art for such low-profile cavity-backed slot antennas but without diminished bandwidth. The present invention meet these needs.
To minimize the limitations in the related art described above, and to minimize other limitations that will become apparent upon reading and understanding the present specification, the present invention discloses a low-profile cavity-backed slot antenna including a cavity substrate having a slot with a resonant frequency and a uniplanar compact photonic band-gap (UC-PBG) substrate proximate to the cavity substrate and having a two-dimensional periodic metallic pattern on a dielectric slab and a ground plane, wherein the UC-PBG substrate behaves substantially as an open boundary at the resonant frequency of the slot, The substrate allows for a reduced cavity size while maintainnig efficient antenna performance.